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While Tesselator can be enjoyed just for itself, Graphito is quite different - more of a tool for the programmer.

Written by the same author, the four main 2D and two 3D programs are unprotected and indeed require the user to enter a short Basic program to make use of the procedures in the main program. For each program there is a two-line header which is listed in the manual with variations to allow you to make more economic use of memory if certain main program resources are not required. Clearly better use of memory allows displays in higher resolution or colour at the expense of the procedures.

Up to 26 procedures are available within the programs and these are accessed by the short programs referred to above. Also included are a series of some three dozen pre-drawn motifs and four alphabets which are called up and manipulated via the procedures. In some of the programs it is possible to alter the motifs (those supplied or your own) from the keyboard or by joystick. Some of the basic motifs 1look rather dull, but even these can be enhanced enormously. Each PROCload routine in the manual is accompanied by a mini screen dump to show what you should get. The 3D programs do provide a degree of hidden surface removal.

Apparently there are exactly seventeen ways in which an asymmetric motif can be arranged to form a two-dimensional network pattern. These are known as wallpaper groups and Graphito will produce them all by regular stepping, mirroring, rotating and 'flopping' - this form of manipulation is not to be confused with tesselation as they do not need to interlock fully, or even at all. Interesting interference patterns can also be built by overlapping two existing designs to make a third.

As I have said, Graphito is more of a tool than an end in itself, and the programs can be incorporated in your own work. Either package could be used to introduce mathematicians to graphics (or vice versa), and indeed the Tesselator manual has a section on the program's use in maths teaching.

Certainly a much better understanding of both program structure and one's own aims are required for Graphito than Tesselator and Graphito's 112 page manual, while comprehensive, will be daunting for the beginner with too many references to points that will be covered later.